How do I convert a moment-rotation angle plot on Abaqus to a moment-curvature plot?

Hello Sir/Ma’am,

I am attempting to solve a bending problem on Abaqus. I have defined a reference point at one end of the structure where I apply my moment. Other end is held fixed. I am able to obtain RM1 and UR1 for the reference point. I need to calculate bending stiffness for my structure, which is the slope of the moment-curvature plot. How do I convert the moment-rotation angle plot to a moment-curvature plot? Please let me know.

I am aware that the derivative of rotation angle w.r.t. the arclength is the curvature (d(theta)/ds). However, since I am looking only at one reference point at one end of my structure, how do I take a derivative in this scenario to convert my moment-rotation angle plot to a moment-curvature plot?

Sincerely,
Ajay